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balance_tracker.go
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balance_tracker.go
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// Copyright 2020 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package server
import (
"sync"
"time"
"github.com/Vigo-Tea/go-ethereum-ant/common/mclock"
"github.com/Vigo-Tea/go-ethereum-ant/ethdb"
"github.com/Vigo-Tea/go-ethereum-ant/les/utils"
"github.com/Vigo-Tea/go-ethereum-ant/p2p/enode"
"github.com/Vigo-Tea/go-ethereum-ant/p2p/enr"
"github.com/Vigo-Tea/go-ethereum-ant/p2p/nodestate"
)
const (
posThreshold = 1000000 // minimum positive balance that is persisted in the database
negThreshold = 1000000 // minimum negative balance that is persisted in the database
persistExpirationRefresh = time.Minute * 5 // refresh period of the token expiration persistence
)
// balanceTracker tracks positive and negative balances for connected nodes.
// After clientField is set externally, a nodeBalance is created and previous
// balance values are loaded from the database. Both balances are exponentially expired
// values. Costs are deducted from the positive balance if present, otherwise added to
// the negative balance. If the capacity is non-zero then a time cost is applied
// continuously while individual request costs are applied immediately.
// The two balances are translated into a single priority value that also depends
// on the actual capacity.
type balanceTracker struct {
setup *serverSetup
clock mclock.Clock
lock sync.Mutex
ns *nodestate.NodeStateMachine
ndb *nodeDB
posExp, negExp utils.ValueExpirer
posExpTC, negExpTC uint64
defaultPosFactors, defaultNegFactors PriceFactors
active, inactive utils.ExpiredValue
balanceTimer *utils.UpdateTimer
quit chan struct{}
}
// newBalanceTracker creates a new balanceTracker
func newBalanceTracker(ns *nodestate.NodeStateMachine, setup *serverSetup, db ethdb.KeyValueStore, clock mclock.Clock, posExp, negExp utils.ValueExpirer) *balanceTracker {
ndb := newNodeDB(db, clock)
bt := &balanceTracker{
ns: ns,
setup: setup,
ndb: ndb,
clock: clock,
posExp: posExp,
negExp: negExp,
balanceTimer: utils.NewUpdateTimer(clock, time.Second*10),
quit: make(chan struct{}),
}
posOffset, negOffset := bt.ndb.getExpiration()
posExp.SetLogOffset(clock.Now(), posOffset)
negExp.SetLogOffset(clock.Now(), negOffset)
// Load all persisted balance entries of priority nodes,
// calculate the total number of issued service tokens.
bt.ndb.forEachBalance(false, func(id enode.ID, balance utils.ExpiredValue) bool {
bt.inactive.AddExp(balance)
return true
})
ns.SubscribeField(bt.setup.capacityField, func(node *enode.Node, state nodestate.Flags, oldValue, newValue interface{}) {
n, _ := ns.GetField(node, bt.setup.balanceField).(*nodeBalance)
if n == nil {
return
}
ov, _ := oldValue.(uint64)
nv, _ := newValue.(uint64)
if ov == 0 && nv != 0 {
n.activate()
}
if nv != 0 {
n.setCapacity(nv)
}
if ov != 0 && nv == 0 {
n.deactivate()
}
})
ns.SubscribeField(bt.setup.clientField, func(node *enode.Node, state nodestate.Flags, oldValue, newValue interface{}) {
type peer interface {
FreeClientId() string
}
if newValue != nil {
n := bt.newNodeBalance(node, newValue.(peer).FreeClientId(), true)
bt.lock.Lock()
n.SetPriceFactors(bt.defaultPosFactors, bt.defaultNegFactors)
bt.lock.Unlock()
ns.SetFieldSub(node, bt.setup.balanceField, n)
} else {
ns.SetStateSub(node, nodestate.Flags{}, bt.setup.priorityFlag, 0)
if b, _ := ns.GetField(node, bt.setup.balanceField).(*nodeBalance); b != nil {
b.deactivate()
}
ns.SetFieldSub(node, bt.setup.balanceField, nil)
}
})
// The positive and negative balances of clients are stored in database
// and both of these decay exponentially over time. Delete them if the
// value is small enough.
bt.ndb.evictCallBack = bt.canDropBalance
go func() {
for {
select {
case <-clock.After(persistExpirationRefresh):
now := clock.Now()
bt.ndb.setExpiration(posExp.LogOffset(now), negExp.LogOffset(now))
case <-bt.quit:
return
}
}
}()
return bt
}
// Stop saves expiration offset and unsaved node balances and shuts balanceTracker down
func (bt *balanceTracker) stop() {
now := bt.clock.Now()
bt.ndb.setExpiration(bt.posExp.LogOffset(now), bt.negExp.LogOffset(now))
close(bt.quit)
bt.ns.ForEach(nodestate.Flags{}, nodestate.Flags{}, func(node *enode.Node, state nodestate.Flags) {
if n, ok := bt.ns.GetField(node, bt.setup.balanceField).(*nodeBalance); ok {
n.lock.Lock()
n.storeBalance(true, true)
n.lock.Unlock()
bt.ns.SetField(node, bt.setup.balanceField, nil)
}
})
bt.ndb.close()
}
// TotalTokenAmount returns the current total amount of service tokens in existence
func (bt *balanceTracker) TotalTokenAmount() uint64 {
bt.lock.Lock()
defer bt.lock.Unlock()
bt.balanceTimer.Update(func(_ time.Duration) bool {
bt.active = utils.ExpiredValue{}
bt.ns.ForEach(nodestate.Flags{}, nodestate.Flags{}, func(node *enode.Node, state nodestate.Flags) {
if n, ok := bt.ns.GetField(node, bt.setup.balanceField).(*nodeBalance); ok && n.active {
pos, _ := n.GetRawBalance()
bt.active.AddExp(pos)
}
})
return true
})
total := bt.active
total.AddExp(bt.inactive)
return total.Value(bt.posExp.LogOffset(bt.clock.Now()))
}
// GetPosBalanceIDs lists node IDs with an associated positive balance
func (bt *balanceTracker) GetPosBalanceIDs(start, stop enode.ID, maxCount int) (result []enode.ID) {
return bt.ndb.getPosBalanceIDs(start, stop, maxCount)
}
// SetDefaultFactors sets the default price factors applied to subsequently connected clients
func (bt *balanceTracker) SetDefaultFactors(posFactors, negFactors PriceFactors) {
bt.lock.Lock()
bt.defaultPosFactors = posFactors
bt.defaultNegFactors = negFactors
bt.lock.Unlock()
}
// SetExpirationTCs sets positive and negative token expiration time constants.
// Specified in seconds, 0 means infinite (no expiration).
func (bt *balanceTracker) SetExpirationTCs(pos, neg uint64) {
bt.lock.Lock()
defer bt.lock.Unlock()
bt.posExpTC, bt.negExpTC = pos, neg
now := bt.clock.Now()
if pos > 0 {
bt.posExp.SetRate(now, 1/float64(pos*uint64(time.Second)))
} else {
bt.posExp.SetRate(now, 0)
}
if neg > 0 {
bt.negExp.SetRate(now, 1/float64(neg*uint64(time.Second)))
} else {
bt.negExp.SetRate(now, 0)
}
}
// GetExpirationTCs returns the current positive and negative token expiration
// time constants
func (bt *balanceTracker) GetExpirationTCs() (pos, neg uint64) {
bt.lock.Lock()
defer bt.lock.Unlock()
return bt.posExpTC, bt.negExpTC
}
// BalanceOperation allows atomic operations on the balance of a node regardless of whether
// it is currently connected or not
func (bt *balanceTracker) BalanceOperation(id enode.ID, connAddress string, cb func(AtomicBalanceOperator)) {
bt.ns.Operation(func() {
var nb *nodeBalance
if node := bt.ns.GetNode(id); node != nil {
nb, _ = bt.ns.GetField(node, bt.setup.balanceField).(*nodeBalance)
}
if nb == nil {
node := enode.SignNull(&enr.Record{}, id)
nb = bt.newNodeBalance(node, connAddress, false)
}
cb(nb)
})
}
// newNodeBalance loads balances from the database and creates a nodeBalance instance
// for the given node. It also sets the priorityFlag and adds balanceCallbackZero if
// the node has a positive balance.
// Note: this function should run inside a NodeStateMachine operation
func (bt *balanceTracker) newNodeBalance(node *enode.Node, connAddress string, setFlags bool) *nodeBalance {
pb := bt.ndb.getOrNewBalance(node.ID().Bytes(), false)
nb := bt.ndb.getOrNewBalance([]byte(connAddress), true)
n := &nodeBalance{
bt: bt,
node: node,
setFlags: setFlags,
connAddress: connAddress,
balance: balance{pos: pb, neg: nb, posExp: bt.posExp, negExp: bt.negExp},
initTime: bt.clock.Now(),
lastUpdate: bt.clock.Now(),
}
for i := range n.callbackIndex {
n.callbackIndex[i] = -1
}
if setFlags && n.checkPriorityStatus() {
n.bt.ns.SetStateSub(n.node, n.bt.setup.priorityFlag, nodestate.Flags{}, 0)
}
return n
}
// storeBalance stores either a positive or a negative balance in the database
func (bt *balanceTracker) storeBalance(id []byte, neg bool, value utils.ExpiredValue) {
if bt.canDropBalance(bt.clock.Now(), neg, value) {
bt.ndb.delBalance(id, neg) // balance is small enough, drop it directly.
} else {
bt.ndb.setBalance(id, neg, value)
}
}
// canDropBalance tells whether a positive or negative balance is below the threshold
// and therefore can be dropped from the database
func (bt *balanceTracker) canDropBalance(now mclock.AbsTime, neg bool, b utils.ExpiredValue) bool {
if neg {
return b.Value(bt.negExp.LogOffset(now)) <= negThreshold
}
return b.Value(bt.posExp.LogOffset(now)) <= posThreshold
}
// updateTotalBalance adjusts the total balance after executing given callback.
func (bt *balanceTracker) updateTotalBalance(n *nodeBalance, callback func() bool) {
bt.lock.Lock()
defer bt.lock.Unlock()
n.lock.Lock()
defer n.lock.Unlock()
original, active := n.balance.pos, n.active
if !callback() {
return
}
if active {
bt.active.SubExp(original)
} else {
bt.inactive.SubExp(original)
}
if n.active {
bt.active.AddExp(n.balance.pos)
} else {
bt.inactive.AddExp(n.balance.pos)
}
}